In the food industry and, in particular, in the beverages industry as well, there has been an increasing tendency for some time to fill foods or beverages, as the case may be, into hollow bodies of thermoplastic plastic, particularly bottles of PET. There are various possibilities for extending the shelf life of beverages, such as hot decanting, for example. If it is desired to fill the beverages that are to be filled into plastic containers, such as PET bottles, for example, in a hot condition, then an elevated temperature-resistance of these containers is necessary.
In known processes and devices for the manufacture of heat-resistant hollow bodies, the preforms are preblown with a medium under pressure (preblowing phase) and, in a second step, are blown into finished form with a medium under higher pressure (final blowing phase). The final blowing pressure is high enough that the plastic molded blank is pressed against the wall of the blow mold. This pressure is maintained for a certain time in order to give the contours the shape that is ideal for the bottle being created. If the hollow bodies that are to be manufactured are temperature-resistant hollow bodies (so-called hot-fill bottles), then the wall of the mold against which the bottle being created is pressed in order to mold the contour is heated. The bottle is held against this warm wall in order to subject the plastic to a partial crystallization in order to thereby achieve an elevated thermal and shape stability. In the event of an excessively great crystallization of the plastic, however, an undesirable discoloration of the same, or opalization, is brought about. In order to achieve a sufficient stability of shape of the bottles upon their removal from the mold and to prevent the above-stated discoloration, it is very important to cool these during the process of manufacturing hot-fillable plastic bottles. The cooling can take place in the interior of the bottle, for example. Various media can be used for that purpose. One widely used technique is cooling by means of compressed air. The cooling or rinsing air, as the case may be, is frequently supplied to the bottle through a hollow stretching rod. In order to guarantee a sufficient cooling by means of air circulation, for example, valves are opened in order to produce an air flow, which transports the heat of the internal wall of the bottle away. So-called rinsing air medium thereby flows from the air feed unit, through the bottle and sound absorber, and into the open air. After this cooling phase, the medium still remaining inside in the bottle and under pressure is discharged. This is also generally carried out through the sound absorber. One disadvantage of this process is the very high consumption of air that is brought about, particularly by the cooling or rinsing process, as the case may be.